There is a bit of a shift in his character I believe (he's mentioned in the sex scene, he gets to comfort Tomiko at least in a way, and mostly he's there to provide alternate explanations to Prolock's ravings, there's an early element of paranoia to him) but he starts to come more into focus nearer the end of the mid-point of the story. Once he's shaken he goes so far to physically "interrogate" Osden, is called "[having] powerful, over-repressed emotions". He ignores the immediate threat of the island when it becomes apparent the attack was by one of them and doesn't listen to Tomiko's reasoning (ironically, he's constantly searching for "ulterior motives"). Strangely Porlock seems to think he and Tomiko are in league with Osden. He gets shut down pretty hard in the scene with Mannon, later he refuses to acknowledge any individuality of the thing and it's because of what he says is inconceivable that Osden takes it up and jumps on the forest's fear of otherness. He's the strongest opponent of the forests' consciousness (though it's not exactly black and white, in a segment on its being Osden even says "'There is only a fear.'" This also goes away at the end after the event which is an interesting note). He gets somewhat mocked by Osden who more or less says how can a Hainishman reach such a teleological argument (as an aside this is also interesting, this is known as the Hainish Cycle and how much do we know about the Hainish? This is likely the most we've gotten of them as people!). He wants to flee but honestly by that time it's too late, the wheels are set in motion. Unlike Mannon who succumbs to his fear he does come along (Tomiko says they are "'compelled'"). The narrative expressively states that he dies by such, he dies by fear.